import java.util.Stack;

class Solution {
    public boolean isValid(String s) {

        Stack<Character> stack = new Stack<>();

        for (int i = 0 ; i < s.length() ; i++) {
            char c = s.charAt(i);
            if (c == '(' || c == '[' || c == '{') {
                stack.push(c);
            }else {
                if (stack.isEmpty()) {
                    return false;
                }
                char topChar = stack.pop();
                if (c == ')' && topChar != '(')
                    return false;
                if (c==']' && topChar != '[')
                    return false;
                if (c=='}' && topChar != '{')
                    return false;
            }
        }
        return stack.isEmpty();
    }
}